Internal combustion engines may be susceptible to undesired detonation, such as engine knock or pre-ignition, under various conditions. Undesired detonation may cause increased pressure build-up and heating that can degrade engine components as well as decrease engine efficiency. As such, various approaches have been used to identify and address knock, including acoustic sensors or accelerometers placed on an engine, as well as internal cylinder pressure sensors and ionization sensors.
In one particular approach, described in US 2003/0230281, a vibration sensor mounted to an engine block identifies engine knock, taking into account noise generated by valve closing events, such as the intake valve. Specifically, the control system attempts to compensate for noise in the vibration sensor caused by the closing of the intake valve in a particular window during which knock is monitored.
The inventors herein have recognized various issues with such an approach. For example, even if the system can identify the valve closing event, the noise generated by such an event still detracts from the signal quality of the vibration sensor with respect to knock detection. Additionally, when valve seating noise is too great, knock detection may not even be possible. As such, knock detection and mitigation may still be compromised.